Fabrication process for a flexible, thin thermal spreader

ABSTRACT

The present invention is a method for fabricating a thermal spreader. The method may include laminating a plurality of layer portions together to fabricate a mechanically flexible substrate. The method may further include providing an internal channel within the mechanically flexible substrate, the internal channel configured for containing an electrically-conductive liquid, the internal channel being further configured to allow for closed-loop flow of the electrically-conductive liquid within the internal channel. The method may further include integrating a pump with the mechanically flexible substrate. The method may further include fabricating a plurality of rigid metal inserts. The method may further include forming a plurality of extension portions on a surface of each rigid metal insert included in the plurality of rigid metal inserts. The method may further include connecting the plurality of rigid metal inserts to the mechanically flexible substrate.

CROSS-REFERENCE

The following patent applications are incorporated by reference in theirentireties:

Express Mail No. Filing Date Ser. No. EM 210498665 US Sep. 12, 200812/283,501 EM 210498682 US Sep. 12, 2008 12/283,504 EM 210498696 US Sep.12, 2008 12/283,502Further, U.S. patent application Ser. No. 12/116,126 entitled: Systemand Method for a Substrate with Internal Pumped Liquid Metal for ThermalSpreading and Cooling, filed May 6, 2008, (pending); U.S. patentapplication Ser. No. 11/508,782 entitled: Integrated Circuit Protectionand Ruggedization Coatings and Methods filed Aug. 23, 2006, (pending);and U.S. patent application Ser. No. 11/732,982 entitled: A Method ForProviding Near-Hermetically Coated Integrated Circuit Assemblies filedApr. 5, 2006 (pending) are also hereby incorporated by reference intheir entirety herein.

FIELD OF THE INVENTION

The present invention relates to the field of thermal management andparticularly to a fabrication process for a flexible, thin thermalspreader.

BACKGROUND OF THE INVENTION

Current fabrication processes for thermal spreaders may not provide athermal spreader having a desired level of performance/desiredperformance characteristics.

Thus, it would be desirable to provide a thermal spreader fabricationprocess which addresses the shortcomings of currently availablesolutions.

SUMMARY OF THE INVENTION

Accordingly, an embodiment of the present invention is directed to amethod for fabricating a thermal spreader, including: laminating aplurality of layer portions together to fabricate a mechanicallyflexible substrate; providing an internal channel within themechanically flexible substrate, the internal channel configured forcontaining an electrically-conductive liquid, the internal channel beingfurther configured to allow for closed-loop flow of theelectrically-conductive liquid within the internal channel; integratinga pump with the mechanically flexible substrate; fabricating a pluralityof rigid metal inserts; forming a plurality of extension portions on asurface of each rigid metal insert included in the plurality of rigidmetal inserts; and connecting the plurality of rigid metal inserts tothe mechanically flexible substrate.

An additional embodiment of the present invention is directed to amethod for fabricating a plurality of thermal spreaders, including:laminating a plurality of layer sheets together to fabricate amechanically flexible substrate sheet; dicing the mechanically flexiblesubstrate sheet to form a plurality of mechanically flexible substrates;providing an internal channel within each mechanically flexiblesubstrate included in the plurality of mechanically flexible substrates,each internal channel configured for containing anelectrically-conductive liquid, each internal channel being furtherconfigured to allow for closed-loop flow of the electrically-conductiveliquid within the internal channel; and integrating a pump with eachmechanically flexible substrate included in the plurality ofmechanically flexible substrates, wherein each mechanically flexiblesubstrate included in the plurality of mechanically flexible substratesis at least partially constructed of organic materials.

A further embodiment of the present invention is directed to a methodfor fabricating a plurality of thermal spreaders, including: laminatinga plurality of layer sheets together to fabricate a mechanicallyflexible substrate sheet; dicing the mechanically flexible substratesheet to form a plurality of mechanically flexible substrates; providingan internal channel within each mechanically flexible substrate includedin the plurality of mechanically flexible substrates, each internalchannel configured for containing an electrically-conductive liquid,each internal channel being further configured to allow for closed-loopflow of the electrically-conductive liquid within the internal channel;integrating a pump with each mechanically flexible substrate included inthe plurality of mechanically flexible substrates; fabricating aplurality of rigid metal inserts; forming a plurality of extensionportions on a surface of each rigid metal insert included in theplurality of rigid metal inserts; and connecting the plurality of rigidmetal inserts to the plurality of mechanically flexible substrates.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not necessarily restrictive of the invention as claimed. Theaccompanying drawings, which are incorporated in and constitute a partof the specification, illustrate embodiments of the invention andtogether with the general description, serve to explain the principlesof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The numerous advantages of the present invention may be betterunderstood by those skilled in the art by reference to the accompanyingfigures in which:

FIG. 1A is a side elevation view of a thermal spreader in accordancewith an exemplary embodiment of the present invention;

FIG. 1B is a sectional view of the thermal spreader of FIG. 1A, saidsectional view showing in enlarged detail extension portions of aninsert of the thermal spreader in accordance with an exemplaryembodiment of the present invention;

FIG. 2A is a side elevation view of a thermal spreader in accordancewith an exemplary embodiment of the present invention;

FIG. 2B is a bottom plan cross-sectional view of the thermal spreadershown in FIG. 2A in accordance with an exemplary embodiment of thepresent invention; and

FIG. 3 is a side elevation view of a thermal spreader assembly inaccordance with an exemplary embodiment of the present invention.

FIG. 4 is a flow chart illustrating a method for fabricating a thermalspreader in accordance with an exemplary embodiment of the presentinvention;

FIG. 5A is an exploded view of a thermal spreader in accordance with anexemplary embodiment of the present invention;

FIG. 5B is a side elevation view of the thermal spreader shown in FIG.5A when assembled;

FIG. 6 is a flow chart illustrating a method for fabricating a thermalspreader in accordance with an exemplary embodiment of the presentinvention;

FIG. 7 is a flow chart illustrating a method for fabricating a pluralityof thermal spreaders in accordance with an exemplary embodiment of thepresent invention;

FIG. 8 is a view illustrating a plurality of layer sheets which may belaminated together to fabricate a mechanically flexible substrate sheet,said substrate sheet being implemented in the fabrication method shownin FIG. 7 in accordance with an exemplary embodiment of the presentinvention;

FIG. 9 is a side elevation view of a thin, mechanically flexible thermalspreader which implements/includes a magnetic pump in accordance with anexemplary embodiment of the present invention;

FIG. 10A is a cross-sectional view of a magnetic pump integrated with amechanically flexible substrate of a thin, mechanically flexible thermalspreader in accordance with an exemplary embodiment of the presentinvention;

FIG. 10B is a bottom plan cross-sectional view of the thermal spreadershown in FIG. 9, said view showing a bottom surface of the ferrouscasing/ferrous lens of the magnetic pump implemented/integrated withsaid thermal spreader in accordance with an exemplary embodiment of thepresent invention;

FIG. 10C is a bottom plan cross-sectional view as in FIG. 10B exceptthat said magnetic pump has been removed to illustrate a slotted portionof the mechanically flexible substrate of the thermal spreader, saidslotted portion configured for receiving the magnetic pump in accordancewith an exemplary embodiment of the present invention;

FIG. 11A is a cross-sectional view of a magnetic pump assembly whichincludes a magnetic pump integrated with a thermally conductive rigidmetal insert in accordance with an exemplary embodiment of the presentinvention;

FIG. 11B is a bottom plan cross-sectional view of a mechanicallyflexible thermal spreader which includes/is integrated with the magneticpump assembly shown in FIG. 11A in accordance with an exemplaryembodiment of the present invention;

FIG. 11C is a bottom plan cross-sectional view as in FIG. 11B exceptthat said magnetic pump assembly has been removed to illustrate aslotted portion of the mechanically flexible substrate of themechanically flexible thermal spreader, said slotted portion configuredfor receiving the magnetic pump assembly in accordance with an exemplaryembodiment of the present invention;

FIG. 12 is a cutaway view of a magnetic pump integrated with an internalchannel of a thermal spreader, said view illustrating a flow directionof electrically-conductive liquid through the internal channel andmagnetic pump, said view further illustrating an ideal electricalcurrent flow/current path relative to said liquid flow direction, saidcurrent flow generated via said electrodes of the thermal spreader;

FIG. 13 is a cutaway view of a magnetic pump integrated with an internalchannel of a thermal spreader, said view illustrating a flow directionof electrically-conductive liquid through the internal channel andmagnetic pump, said view further illustrating a curved electricalcurrent flow/current path relative to said liquid flow direction, saidcurrent flow generated via said electrodes of the thermal spreader;

FIG. 14 is a cutaway view of a magnetic pump in accordance with anexemplary embodiment of the present invention, integrated with aninternal channel of a liquid cooling loop of a mechanically flexiblesubstrate of a thin mechanically flexible thermal spreader, saidmagnetic pump including a plurality of magnet flow channels/dielectricflow straightener channels separated by channel walls, said view furtherillustrating a current path produced when said magnetic pump of thepresent invention is implemented as shown;

FIG. 15A is a side elevation view of a flexible liquid cooling loop forproviding a thermal path between a heat source surface and heat sinksurface in accordance with an exemplary embodiment of the presentinvention;

FIG. 15B is a cross-sectional view of a mechanically rigid tubingsection of the flexible liquid cooling loop shown in FIG. 15A inaccordance with an exemplary embodiment of the present invention;

FIG. 15C is a side elevation view of the flexible liquid cooling loopshown in FIG. 15A being in thermal contact with a heat source and a heatsink in accordance with an exemplary embodiment of the presentinvention;

FIG. 15D is a side elevation view of a flexible liquid cooling loopwhich includes a thermoelectric generator, said flexible liquid coolingloop shown as being in thermal contact with a heat source and a heatsink in accordance with an exemplary embodiment of the presentinvention;

FIG. 16 is a side elevation view of a flexible liquid cooling loop beingimplemented as a thermal bridge between an electronics component of avehicle and a mounting plate of the vehicle when said electronicscomponent is mounted to said mounting plate via vibration isolators inaccordance with an exemplary embodiment of the present invention;

FIG. 17A is a top plan view of a flexible liquid cooling loop having a“watchband” configuration in accordance with an exemplary embodiment ofthe present invention;

FIG. 17B is a side elevation view of the flexible liquid cooling loopshown in FIG. 17A in accordance with an exemplary embodiment of thepresent invention;

FIG. 18A is a top plan view of a flexible liquid cooling loop having a“racetrack” configuration in accordance with an exemplary embodiment ofthe present invention;

FIG. 18B is a side elevation view of the flexible liquid cooling loopshown in FIG. 18A in accordance with an exemplary embodiment of thepresent invention;

FIG. 19A is a top plan view of a liquid cooling loop in accordance withan alternative exemplary embodiment of the present invention;

FIG. 19B is a side elevation view of the liquid cooling loop shown inFIG. 19A in accordance with an exemplary embodiment of the presentinvention;

FIG. 19C is a cross-sectional view of a mechanically rigid tubingsection of the liquid cooling loop shown in FIGS. 19A and 19B inaccordance with an exemplary embodiment of the present invention;

FIG. 20 is a sectional view of an internal channel of a mechanicallyflexible substrate of a thermal spreader, said internal channelconnected to an expandable bladder, said internal channel including awall (shown in phantom-line view) for directing fluid flow within thechannel towards said bladder in accordance with a further exemplaryembodiment of the present invention;

FIG. 21A is a sectional view of an internal channel of a mechanicallyflexible substrate of a thermal spreader in which the expandable bladderis placed on an interior wall of the internal channel in accordance withan exemplary embodiment of the present invention;

FIG. 21B is a sectional view of an internal channel of a mechanicallyflexible substrate of a thermal spreader in which the expandable bladderis placed on an exterior wall of the internal channel in accordance withan alternative exemplary embodiment of the present invention;

FIG. 22A is a bottom plan cross-sectional view of a mechanicallyflexible substrate having a microchannel fabricated into the substratevia film-based photoresists in accordance with a further exemplaryembodiment of the present invention;

FIG. 22B is a side elevation view of the mechanically flexible substrateshown in FIG. 22A in accordance with an exemplary embodiment of thepresent invention; and

FIG. 23 is a bottom plan cross-sectional view of a mechanically flexiblesubstrate which is configured for minimizing a channel-to-chassisinterconnect for the substrate in accordance with an exemplaryembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the presently preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings.

A thermal spreader/heat spreader may be used to diffuse and transportthermal energy from a heat source, such as an electronics component on acircuit board, to a lower temperature surface, such as a chassis inwhich the circuit board may be mounted. A heat spreader may beconstructed of a material having a high thermal conductivity, such asmetal (ex.—copper, aluminum), in order to reduce thermal gradientswithin the heat spreader so that the heat spreader may minimize thetemperature of the heat source. When thermal gradients within a heatspreader are excessive, inserts (ex.—heat pipes, pyrolytic graphiteinserts) having high effective thermal conductivities may be integratedwith/into the heat spreader to offer/provide improved thermal paths.

Because of their structural properties, metal heat spreaders may berigid (ex.—mechanically inflexible). Due to tolerance uncertaintieswhich may be associated with an assembly that includes a heat spreader,a chassis, and a circuit board, the heat spreader of said assembly maybe designed for some tolerance stack-up in order to prevent subjectingan electronics component (which may be connected to the circuit board)to forces which may be generated by a tight or interference fit betweenthe heat spreader and the electronics component. Alternatively, anon-metal heat spreader may be implemented and may provide improvedmechanical flexibility compared to a metal heat spreader. However, anon-metal heat spreader may have an extremely low thermal conductivityrelative to a metal heat spreader, and thus, may not be a suitableoption.

The rigid, metal heat spreader may also be implemented with a compliantthermal gap filler/thermal interface material. The thermal interfacematerial may be placed between the metal heat spreader and anelectronics component to ensure that a non-air conduction path existsbetween a surface of the metal heat spreader and a surface of theelectronics component. The thermal interface material/compliant materialmay generally be organic-based and may have a thermal conductivity whichmay be approximately two orders of magnitude lower than the thermalconductivity of the metal of the metal heat spreader. Thus, the thermalinterface material may contribute a significant portion of an overallthermal resistance path between the electronics component and an ambientenvironment.

A number of basic metals which may be used in metal heat spreaders mayhave thermal conductivities of about 100-400 Watts/meters•Kelvin (W/mK).Heat pipes and exotic materials, such as graphite and diamond, which maybe integrated with heat spreaders may exhibit effective thermalconductivities of up to approximately ten times greater than 100-400(W/mK). As power dissipation from electronic components continues toincrease, it may be desirable to construct heat spreaders/to implementthermal spreading technologies which provide higher effective thermalconductivities. However, the suitability for use of certain materialswhen constructing heat spreaders/implementing thermal spreadingtechnologies may be limited by factors such as heat flux limits (ex.—forheat pipes), orthotropic properties (ex.—of graphite), or cost (ex.—ofdiamond). Therefore, it may be desirable to implement a heat spreadertechnology which produces/provides a heat spreader that is: a.)mechanically flexible; b) has an effective thermal conductivity which issignificantly higher than the effective thermal conductivities ofcurrently available rigid, metal heat spreaders or heat pipe assemblies;and c.) has heat flux limits which are significantly higher than theheat flux limits of currently available rigid, metal heat spreaders orheat pipe assemblies.

Referring generally to FIGS. 1A through 2B, a heat spreader/thermalspreader in accordance with an exemplary embodiment of the presentinvention is shown. The thermal spreader 100 may include a mechanicallyflexible substrate 102. In exemplary embodiments, the substrate 102 maybe at least partially (ex.—primarily) constructed/fabricated of flexibleor mechanically compliant materials. For example, the substrate 102 maybe at least partially constructed of organic materials. Further, thesubstrate 102 may be at least partially constructed of organic-inorganiccomposite materials which may include glass, ceramics, carbon, metalreinforcements, thin metallic sheets, molded plastic materials, standardcircuit board materials, flexible circuit board materials, rigid-flexcircuit cards, and/or the like. Constructing the substrate 102 at leastpartially of organic materials (rather than constructing a thermalspreader entirely of metal) may provide a thermal spreader 100 which ismechanically flexible, lightweight and low cost.

As described above, because the mechanically flexible substrate 102 ofthermal spreader 100 is made of/includes regions of a compliantmaterial, it may be sufficiently flexible so that it may bend andthereby make up much if not all of any dimensional gaps between a heatsource/heat source region and a heat sink/heat sink region due totolerance stack-up, thermal expansion effects, vibration, etc. Forinstance, the substrate 102 of the thermal spreader 100 may beconfigured to bend to a sufficient degree such that it may contact twoor more surfaces that have a varying mechanical separation in adirection perpendicular to a plane of the substrate 102 due to tolerancestackup, vibration, thermal expansion, etc. Such flexibility of thesubstrate 102 of the thermal spreader 100 may promote a reduced need forutilizing compliant thermal gap filling materials (ex.—thermal pads,gels) that may otherwise be needed to provide compliance, said compliantthermal gap filling materials also typically representing a significantthermal resistance.

In further embodiments, the mechanically flexible substrate 102 may format least one internal channel/flow channel 104. The internal channel 104may be configured for containing an electrically-conductive liquid. Inexemplary embodiments, the internal channel 104 may provide for/mayallow closed-loop, flow of the electrically-conductive liquid (ex.—theinternal channel 104 may be/may include an internal/embedded coolingloop). In exemplary embodiments, the electrically-conductive liquid maybe/may include a liquid metal and/or a liquid metal alloy. For example,the liquid metal alloy may include at least two of the following:Gallium, Indium, Tin, Zinc, Lead and Bismuth. For instance, the liquidmetal alloy may be a Gallium-Indium-Tin eutectic known as Galinstan. Infurther embodiments, the electrically-conductive liquid may include ametal having a melting temperature of less than fifty (50) degreesCelsius. In additional embodiments, the substrate 102 may include one ormore mechanically compliant layers, such as a first mechanicallycompliant layer 106 and a second mechanically compliant layer 108.Further, the internal channel/internal cooling loop 104 may be formedby/formed between/embedded between the first compliant layer 106 and thesecond compliant layer 108.

In current embodiments of the present invention, the thermal spreader100 may further include a mechanism for circulating theelectrically-conductive liquid/fluid, such as at least one pump 110. Thepump 110 may be configured for being connected to/integrated with thesubstrate 102. The pump 110 may be further configured for circulatingthe flow of/moving the electrically-conductive liquid within theinternal channel 104 so that the thermal spreader 100 may provide a higheffective thermal conductivity between heat source(s) (ex.—electronicscomponent(s) on a circuit board) to which the thermal spreader 100 maybe connected/attached, and heat sink(s) (ex.—a chassis/chassis rail(s)in/on which the electronics component/circuit board may be mounted) towhich the thermal spreader 100 may be connected/attached. In this way,the thermal spreader 100 may be configured for directing thermal energyfrom the heat source to the heat sink via the electrically-conductiveliquid. In exemplary embodiments, the pump 110 may be a piezoelectricpositive displacement pump, an inductive pump, a magnetic pump (ex.—asolid state magnetic pump), or the like.

In further embodiments, the thermal spreader 100 may include one or morelocalized, high thermal conductivity/thermally-conductive, rigid metalinserts 112. Each insert 112 may be configured for being connectedto/integrated with/received by (ex.—such as via slots formed by thesubstrate)/placed within the mechanically flexible substrate 102 suchthat the insert 112 may be in thermal contact with theelectrically-conductive liquid and the substrate 102. Further, eachinsert 112 may be further configured for promoting heat transfer betweenthe thermal spreader 100 and the electrically-conductive liquid (ex.—forpromoting thermal energy transfer/local heat transfer to/into andfrom/out of the electrically-conductive liquid/coolant). In additionalembodiments, each insert 112 may include a first surface 114 and asecond surface 116, the first surface 114 being located generallyopposite the second surface 116. The first surface/internal surface 114may be configured for being oriented toward the internal channel 104(ex.—oriented so as to physically contact the electrically-conductiveliquid). The second surface/external surface 116 may be configured forbeing oriented away from the internal channel 104 (ex.—oriented so as tonot physically contact the liquid).

In current embodiments of the present invention, the first surface 114of each insert 112 may be configured with one or more mechanicalfeatures/fine features/roughened areas/machined areas/extendedsurfaces/extension portions 118. The extension portions 118 may promotethermal energy transfer between the insert 112 and theelectrically-conductive liquid by providing increased or additionalcontact surface area/thermal contact area/convective heat transfer area,thereby reducing convective thermal resistance between the insert 112and the liquid. The insert 112 may be fabricated with the extensionportions 118 via manufacturing processes, such as machining, extrusion,chemical etching, or the like. For instance, the extension portions 118may be fins, pins, or plates which may be aligned with a direction offlow of the liquid, or said extension portions 118 may be other suitablegeometries for increasing the heat transfer area of the insert 112and/or for creating localized turbulence to provide higher levels ofheat transfer. The fine features/roughened areas/extension portions 118may be produced via machining, roughening, machining extrusion, chemicaletching, molding, or other like processes. Further, the extensionportions 118 of the inserts 112 may allow the inserts 112 to providestructural support for the compliant layers (106, 108) of themechanically flexible substrate 102, said compliant layers (106, 108)sandwiching or being positioned on each side of (ex.—above and below)the internal channel 104. In still further embodiments, the secondsurface/external surface 116 of the insert 112 may be smooth forpromoting minimization of contact resistance.

In further embodiments, each insert 112 may be at least partiallyconstructed of/may be integrated with thermally-conductive foam, anarray of carbon nanotubes, high thermal-conductivity filaments, and/orthe like, for providing additional heat transfer surfaces/thermalenhancements for the thermal spreader 100. For example, thethermally-conductive foam may be a graphite foam, a graphite alloy foam,and/or a copper alloy foam.

When implementing/during application of electrically conductive liquidcooling (such as via the internal channel 104/cooling loop describedabove), a possible limiting issue may be the potential forchemical/metallurgical interactions between metals of/within the thermalspreader 100 and the liquid. In order to maximize thermal performance ofthe thermal spreader 100, it may be imperative that theelectrically-conductive liquid have good thermal contact with the metalinserts 112 of/within the thermal spreader 100. However, metallurgicalor chemical interactions between metal(s) of the thermal spreader 100(ex.—metals of the substrate 102 and/or the inserts 112) and theelectrically-conductive liquid may lead to corrosion of said metal(s) ofthe thermal spreader 100 into the liquid, which may result in changes inthe properties of the liquid. If the liquid is a metal alloy, additionalmetals which corrode into the liquid may result in the formation of anew metal alloy in the liquid. This new metal alloy may be highlycorrosive and/or may include a high melting temperature metal. Forexample, when Gallium-containing alloys are brought into contact withAluminum, the Gallium may rapidly diffuse into the Aluminum, therebyresulting in the formation of a highly corrosive alloy, particularlywhen in the presence of moisture. Further, Gallium, Indium and Tin maytend to have high diffusion coefficients into metals such as Gold,Copper, and Silver, which may result in the production of high meltingtemperature alloys upon diffusion and alloy formation.

A possible solution to the above-referenced problem may involveapplying/plating Nickel to the thermal spreader 100 (ex.—to the metalinserts 112 of the thermal spreader 100) to protect the thermal spreader100 from corrosion. However, this solution may be expensive, the Nickelmay represent a thermal resistance, and the Nickel may still react withthe liquid. A further possible solution may involveevaporation/sputtering/chemical vapor deposition/plating of materialssuch as Tantalum, Tungsten, other inorganic coatings, and/or organiccoatings (ex.—Parylene) onto the thermal spreader 100 via a vapordeposition process(es). Although application of such materials mayprovide a suitable barrier, said vapor deposition processes using saidmaterials may be expensive and/or complicated to perform. The presentinvention addresses the above-referenced problem by providing a thermalspreader 100 which may have a protective barrier between theelectrically-conductive liquid and metal surfaces of the thermalspreader 100 (ex.—metal portions of the flexible substrate which maycontact/may otherwise contact said liquid, the surfaces of the metalinserts 112 which may contact/may otherwise contact said liquid).Further, the protective barrier/coating provided by the presentinvention may be a non-metallic coating (ex.—alkali silicate glass) thatis extremely thin, provides minimal thermal resistance, while providingsuperior long term protection/preventing electrochemical reactionsbetween metal surfaces of the thermal spreader 100 and theelectrically-conductive liquid.

In exemplary embodiments, the first surface/internal surface 114(ex.—the surface oriented toward/more proximal to/so as to contact theliquid) of each insert 112 may be at least partially coated with one ormore layers of a protective coating, such as alkali silicate glass. Forexample, a layer included in the one or more layers of alkali silicateglass may have a thickness value ranging between and including thevalues of 0.1 microns and 10.0 microns. In additional embodiments, othersurfaces/portions of the thermal spreader 100 (ex.—fine features on theinterior/first surface 114 of each insert 112, such as the extensionportions 118, which may be configured for being positioned/located atheat source and heat sink locations) may also be at least partiallycoated with the protective alkali silicate glass coating. The alkalisilicate glass of the present invention may have one or more of a numberof various compositions, including but not limited to those compositionsdescribed in U.S. patent application Ser. No. 11/732,982, filed on Apr.5, 2007, entitled: “A Method For Providing Near-Hermetically CoatedIntegrated Circuit Assemblies”; U.S. patent application Ser. No.11/508,782, filed on Aug. 23, 2006, entitled: “Integrated CircuitProtection and Ruggedization Coatings and Methods”; and/or U.S. patentapplication Ser. No. 12/116,126, filed on May 6, 2008, entitled: “Systemand Method for a Substrate with Internal Pumped Liquid Metal for ThermalSpreading and Cooling”, which are herein incorporated by reference.

In exemplary embodiments of the present invention, the alkali silicateglass (ASG) layers may be easily deposited implementing standardatmosphere/near room temperature processes, thereby allowing for lowrecurring cost/low capital investment processing methods. For instance,the alkali silicate glass may be applied by spraying one or more layersof the material/ASG onto the thermal spreader 100 via an Asymtek®jetting system and an appropriate spray head. Alternatively, the alkalisilicate glass coating may be applied by flooding the internalchannel(s) 104 with a solution of the ASG coating and then utilizingforced air to remove any excess ASG coating/solution. In furtherembodiments, appropriately passivated electrodes (ex.—electrodes coatedwith/constructed entirely of a passivation metal such as Tungsten,Tantalum, or Nickel) may be inserted into/integrated with themechanically flexible substrate 102 post-treatment (ex.—after the ASGcoating is applied). Still further, the electrodes may be constructed ofgraphite or another properly coated metal, such as Tantalum, Tungsten,or Nickel. The electrodes may be configured for generating an electricalcurrent flow through the electrically-conductive liquid via an appliedvoltage to said electrodes. In further embodiments, the thermal spreader100/surfaces of the thermal spreader which may contact theelectrically-conductive liquid may be at least partially coated with asubstance which may improve wetting characteristics for the liquid.

As mentioned above, the thermal spreader 100 of the present inventionmay be configured for providing a high effective thermal conductivitybetween a heat source and a heat sink. The thermal spreader 100 may beimplemented in a variety of applications. For example, the thermalspreader 100 of the present invention may be implemented as part of athermal spreader assembly 300 as shown in FIG. 3. In exemplaryembodiments, the thermal spreader assembly 300 may include a heatsource, such as a conduction-cooled circuit card assembly 302. Theconduction-cooled circuit card assembly 302 may include a circuit card304. The circuit card assembly 302 may further include an electroniccomponent 306 mounted on the circuit card 304. The circuit card assembly302 may further include a plurality of mechanical mounting fixtures(ex.—wedge locks, card guides, etc.) 308 mounted on said circuit card304. The thermal spreader assembly 300 may further include a thermalspreader 100 as described above. The thermal spreader 100 may beconfigured for being thermally connected to the circuit card 304 and theelectronic component 306, such as via a layer of thermal adhesive 310.The thermal spreader 100 may be further configured for being thermallyconnected to a heat sink, such as a chassis/electronics housing, bybeing mounted in the chassis (ex.—on rails of the chassis) via themechanical mounting fixtures/mounting feature(s) 308. The thermalspreader 100 is configured for providing thermal conductivity betweenthe heat source (ex.—the electronic component 306) and the heat sink(ex.—the chassis). The mechanical compliance of the thermal spreader 100of the present invention may allow for a thermal spreader assembly 300which has a reduced need for thermal gap filler, is lighter weight andlower in cost than thermal spreader assemblies which implement amechanically rigid thermal spreader (ex.—a thermal spreader constructedentirely of metal).

FIG. 4 illustrates a method for fabricating/producing/providing athermal spreader in accordance with an exemplary embodiment of thepresent invention. The method 400 may include the step of fabricating amechanically flexible substrate 402. As mentioned above, at least aportion of the mechanically flexible substrate may be constructed oforganic material. The method 400 may further include the step ofproviding an internal channel within the mechanically flexible substrate403. The internal channel may be configured for containing anelectrically-conductive liquid and may be further configured to allowfor closed-loop flow of the electrically-conductive liquid within theinternal channel. For example, the internal channel may be provided byforming the internal channel within the mechanically flexible substrate(ex.—the internal channel may be a recess/groove/slotted recess formedwithin the mechanically flexible substrate, as shown in FIG. 5A) or byintegrating the internal channel/flow loop within the mechanicallyflexible substrate (ex.—the flow loop/internal channel may be a separatecomponent connected to/integrated within/received within/accommodated bythe mechanically flexible substrate). The method 400 may further includethe step of integrating a pump with the mechanically flexible substrate404. For example, as described above, the pump may be configured forcirculating the electrically-conductive liquid within the internalchannel.

The method 400 may further include the step of fabricating a pluralityof rigid metal inserts 406. For instance, as discussed above, each rigidmetal insert may be configured for being integrated with themechanically flexible substrate for promoting the transfer of thermalenergy both to and from the electrically conductive liquid. As describedabove, the thermal spreader is configured for being connected to a heatsource and a heat sink, and is further configured for directing thermalenergy from the heat source to the heat sink via theelectrically-conductive liquid. The method 400 may further include thestep of forming a plurality of extension portions on a surface of eachrigid metal insert included in the plurality of rigid metal inserts 408.For instance, as described above, said extension portions may beconfigured for promoting thermal energy transfer between the rigid metalinsert and the electrically-conductive liquid. The method 400 mayfurther include the step of connecting the plurality of rigid metalinserts to the mechanically flexible substrate 410.

The method 400 may further include the step of coating a metal portionof an electrically-conductive liquid contact surface of the mechanicallyflexible substrate with a layer of alkali silicate glass 412. The method400 may further include the step of coating an electrically-conductiveliquid contact surface of each rigid metal insert with a layer of alkalisilicate glass 414. The method 400 may further include the step ofintegrating a plurality of passivation metal-coated electrodes with themechanically flexible substrate 416. As discussed above, said electrodesmay be configured for generating an electrical current flow through theelectrically-conductive liquid via an applied voltage to saidelectrodes.

As discussed above, thermal spreaders may be used for diffusing thermalenergy from heat sources and for transporting the thermal energy to alocation at which the thermal energy (ex.—heat) may be dissipated. Forinstance, the thermal spreader may be used in electronics to remove heatfrom a high power electronic component which may be connected to acircuit board, and to conduct said heat/thermal energy to the walls of achassis in which the circuit board/circuit card is mounted/enclosed. Anumber of thermal spreaders may be custom-designed/fabricated for usewith a particular circuit card assembly and/or may utilize thermal gapfiller for providing a thermal path between a power-dissipatingcomponent on a circuit card assembly and the thermal spreader. Further,as previously discussed, a number of thermal spreaders may be made ofmetals and may be expensive to produce due to: a.) high energy costsassociated with processing the metals; b.) the processing time requiredfor machined parts; and/or c.) the tooling costs for providing cast orextruded thermal spreaders.

In contrast to metal thermal spreaders (which utilize conduction) orthermal spreaders implementing heat pipes (which utilize a vaporpressure/capillary force-driven fluid flow), the thermal spreader 100 ofthe present invention utilizes a pumped, electrically-conductive liquidfor transporting thermal energy. The thermal spreader 100 of the presentinvention implements an approach which may serve to separate the thermaltransport mechanism from the structure/structural mechanism, therebyproviding good thermal conduction even though the mechanically flexiblethermal spreader 100 may be constructed of organic (ex.—mechanicallyflexible) materials.

Referring generally to FIGS. 5A and 5B, a thermal spreader 500 inaccordance with a further exemplary embodiment of the present inventionis shown. The thermal spreader 500 may include a mechanically flexiblesubstrate 502. The mechanically flexible substrate 502 may be formedof/may include multiple layer portions. For example, the substrate 502may be constructed as a 3-layer portion configuration in which amiddle/second layer portion 504, which forms/includes an internalchannel 506 for containing electrically-conductive liquid, is“sandwiched” between a top/first layer portion 508 and a bottom/thirdlayer portion 510. In additional embodiments, the bottom layer portion510 may form a plurality of recesses 512 (ex.—slots) configured forallowing the bottom layer portion 510 to integrate with (ex.—receive) aplurality of metallic, high thermal conductivity inserts 514. Saidinserts 514 may be configured for providing localized higher heat fluxat heat source and/or heat sink locations. In still further embodiments,one or more of the layers (504, 508, 510) may be constructed of organicmaterials, inorganic materials, or the like for providing themechanically flexible substrate 502, which may be a low-profile/thinsubstrate. For instance, said materials may include standard circuitboard materials, rigid-flex materials, and/or the like.

Referring to FIG. 6, a method for providing/fabricating/producing saidthermal spreader 500 is shown. In an exemplary embodiment, the method600 may include the step of laminating the plurality of layer portionstogether to fabricate the mechanically flexible substrate 602. Asmentioned above, the mechanically flexible substrate may be at leastpartially constructed of thin, organic material. The method 600 mayfurther include the step of providing an internal channel within themechanically flexible substrate 603. The internal channel may beconfigured for containing an electrically-conductive liquid and may befurther configured to allow for closed-loop flow of theelectrically-conductive liquid within the internal channel. The method600 may further include the step of integrating a pump with themechanically flexible substrate 604. For example, as described above,the pump may be configured for circulating the electrically-conductiveliquid within the internal channel.

The method 600 may further include the step of fabricating a pluralityof rigid metal inserts 606. For instance, as discussed above, each rigidmetal insert may be configured for being integrated with themechanically flexible substrate for promoting the transfer of thermalenergy both to and from the electrically conductive liquid. As describedabove, the thermal spreader is configured for being connected to a heatsource and a heat sink, and is further configured for directing thermalenergy from the heat source to the heat sink via theelectrically-conductive liquid. The method 600 may further include thestep of forming a plurality of extension portions on a surface of eachrigid metal insert included in the plurality of rigid metal inserts 608.For instance, as described above, said extension portions may beconfigured for promoting thermal energy transfer between the rigid metalinsert and the electrically-conductive liquid.

The method 600 may further include the step of connecting the pluralityof rigid metal inserts to the mechanically flexible substrate 610. Forexample, as discussed above, the inserts may be received by/connected tothe substrate via recesses formed by the substrate. The method 600 mayfurther include the step of coating a metal portion of anelectrically-conductive liquid contact surface of the mechanicallyflexible substrate with a layer of alkali silicate glass 612. The method600 may further include the step of coating an electrically-conductiveliquid contact surface of each rigid metal insert included in theplurality of rigid metal inserts with a layer of alkali silicate glass614. The method 600 may further include the step of integrating aplurality of passivation metal-coated electrodes with the mechanicallyflexible substrate 616. As discussed above, said electrodes may beconfigured for generating an electrical current flow through theelectrically-conductive liquid via an applied voltage to saidelectrodes.

Referring to FIG. 7, a method 700 for providing/fabricating/producing aplurality of thermal spreaders 500 via additive manufacturing/built-upprocessing/sequential addition processing/parallel processing/batchprocessing is shown. In an exemplary embodiment, the method 700 mayinclude the step of laminating a plurality of layer sheets together tofabricate a mechanically flexible substrate sheet 702. For example, asshown in FIG. 8, a first layer sheet 802, which may include a pluralityof top/first layer portions 508, a second layer sheet 804, which mayinclude a plurality of middle/second layer portions 504, and a thirdlayer sheet 806, which may include a plurality of bottom/third layerportions 510 may be laminated together to fabricate a mechanicallyflexible substrate sheet 800. For instance, fabrication of themechanically flexible substrate sheet may be performed usingconventional circuit board manufacturing processes. In furtherembodiments, the method 700 may further include the step of dicing themechanically flexible substrate sheet to form a plurality ofmechanically flexible substrates 704. As mentioned above, eachmechanically flexible substrate may be at least partially constructed ofa range of thin, organic materials. The mechanically flexible substratemay also be partially constructed of inorganic materials. The method 700may further include providing an internal channel within eachmechanically flexible substrate included in the plurality ofmechanically flexible substrates 705. For example, each internal channelmay be configured for containing an electrically-conductive liquid andmay be further configured to allow for closed-loop flow of theelectrically-conductive liquid within the internal channel.

In additional embodiments, the method 700 may further include the stepof integrating a pump with each mechanically flexible substrate includedin the plurality of mechanically flexible substrates to form a pluralityof thermal spreaders 706. For example, each individual mechanicallyflexible substrate may be integrated with its own corresponding pump toform a thermal spreader. Still further, the method 700 may furtherinclude the step of fabricating a plurality of rigid metal inserts 708.The method 700 may further include the step of forming a plurality ofextension portions on a surface of each rigid metal insert included inthe plurality of rigid metal inserts 710. The method 700 may furtherinclude the step of connecting the plurality of rigid metal inserts tothe plurality of mechanically flexible substrates 712.

In exemplary embodiments, the method 700 may further include the step ofcoating a metal portion of electrically-conductive liquid contactingsurfaces of each mechanically flexible substrate included in theplurality of mechanically flexible substrates with a layer of alkalisilicate glass 714. The method 700 may further include the step ofcoating an electrically-conductive liquid contacting surface of eachrigid metal insert included in the plurality of rigid metal inserts witha layer of alkali silicate glass 716. The method 700 may further includethe step of integrating a plurality of passivation metal-coatedelectrodes with each mechanically flexible substrate included in theplurality of mechanically flexible substrates 718. In this way,manufacture of the plurality of thermal spreaders may be performed via alow cost, batch processing methodology, utilizing low cost materials.Further said thermal spreaders produced via such methods may belightweight and suitable for use in weight and size consciousapplications, such as airborne electronics and portable consumerelectronics (such as laptop computers).

Localized forced convection cooling may be applied for thermalmanagement of electronics. For example, a computer may implement one ormore fans for cooling purposes. However the moving parts of the fans maybe potential weak links with regards to overall system reliability.Solid-state pumps may be used in liquid cooled systems which demand veryhigh reliability. For instance, one method of solid-state pumping mayinvolve application of a magnetic field in combination with an electriccurrent for applying a pumping force to the liquid/fluid of the liquidcooled system. This magnetic pumping method may require that said liquidhave a high electrical conductivity, so liquid metal or any other liquidwith sufficiently high electrical conductivity may be implemented. Thepresent invention provides a solid-state mechanism for pumpingelectrically conductive liquids within a thin, mechanically flexiblethermal spreader.

As described above, a magnetic pump, such as a solid-state magnetic pumpmay be implemented for circulating electrically-conductive liquid withinthe mechanically flexible substrate of the thermal spreader of thepresent invention. Referring generally to FIGS. 9, 10A and 10B, anexemplary embodiment of a thermal spreader 900 of the present inventionis shown which includes/implements a magnetic pump 110. As previouslydiscussed, the thermal spreader 900 may be a thin, flexible thermalspreader which includes/forms an electrically conductive liquid coolingloop/internal channel 104. Further, the thermal spreader 900 may beconfigured with embedded electrodes 902. A voltage may be applied acrossthe electrodes 902 for generating a current flow through theelectrically conductive liquid.

In current embodiments of the present invention, the thermal spreader900/pump 110 may be configured with one or more magnets 904. Further,the pump 110 may include a casing, which may, for instance, beconstructed of ferrous material (ex.—a ferrous lens 906). Each magnet904 may be connected to/integrated with/enclosed within/encased by theferrous lens 906. In exemplary embodiments, when the pump 110 isconnected to the mechanically flexible substrate 908 of the thermalspreader 900, the magnets 904 may be positioned/located on oppositesides of the internal channel 104 (as shown in FIG. 10A. The ferrouslens 906 is configured for maximizing the pumping power of the pump 110and for focusing magnetic flux. The pump 110 further provides a lowprofile liquid pumping mechanism which may be added/connectedto/integrated with the mechanically flexible substrate 908/thermalspreader 900, while still allowing the thermal spreader 900 to remainmechanically flexible. FIG. 10C illustrates that the thermal spreader900/mechanically flexible substrate 908 may include/may form a slottedportion 910 for allowing the pump 110 to be connected to/received by thethermal spreader 900 and for allowing the ferrous lens 906 to passthrough/be received so that said ferrous lens may fully contain amagnetic field generated within the thermal spreader 900.

In further embodiments, the pump 110 may be configured for beingintegrated with a rigid metal insert 912 to form a magnetic pumpassembly/pump-rigid metal insert assembly 914, as shown in FIGS. 11A and11B. In an exemplary embodiment, a thermal spreader 1100 may be providedwhich includes the pump-rigid metal insert assembly 914. For instance,the pump-rigid metal insert assembly 914 may be configured for beingconnected to a mechanically flexible substrate 1102 of the thermalspreader. The substrate 1102 may include/form a slotted portion 1104 (asshown in FIG. 11C) for receiving/connecting with the pump-rigid metalinsert assembly 914. The rigid metal insert 912 may be configured forpromoting heat transfer between the thermal spreader 1100 and theelectrically-conductive liquid (ex.—for promoting thermal energytransfer/local heat transfer to/into and from/out of theelectrically-conductive liquid/coolant). Further, the pump 110 may beconstructed of a thermally conductive material (ex.—metal) which may, incombination with the metal of the insert 912, allow for the pump-rigidmetal insert assembly 914 to provide thermal conduction/thermalspreading properties to the thermal spreader 1100 of the presentinvention. The ferrous lens 906 may form/may include one or more vias916 which may be at least partially filled with thermally-conductivematerial for promoting increased local thermal conductivity of thepump-rigid metal insert assembly 914.

When implementing a magnetic pump with an electrically-conductivecooling loop, a current path (generated via the electrodes) through themoving liquid in a uniform or non-uniform magnetic field may be an arc,rather than following a straight line. If the arc bridges outside of themagnetic field, the efficiency of the pump may be significantly reduced,which may result in lower fluid flow rates and/or pressure head. As themagnetic pump is miniaturized, the effects of the non-uniform magneticfield may become more significant.

For the pump 110 implemented in the present invention, the force inducedon the electrically-conductive liquid may be due to current flowingthrough the liquid between the electrodes 902. The effective electricalimpedance of the electrically-conductive liquid may be a function of theapplied magnetic field. In an ideal system, a constrained, straight-linecurrent path in a uniform magnetic field resulting in a uniform force onthe liquid metal across the internal channel 104 would occur, as shownin FIG. 12. However, in practice, the magnetic field (and therefore theimpedance) may generally not be uniform and the current path maygenerally not be a straight line due to the continuous force on theelectrons normal to the direction of the current. Variation in magneticflux across the internal channel 104/pump channel may also contribute tothe deviation in current path and subsequent pump head pressurenon-uniformity. In a system, considering/assuming a uniform magneticfield is applied, the current path may generally flow in an arc ratherthan a straight line. Under worst case conditions, current flow mayoccur at regions beyond the magnetic field and may thus produce reducedpumping force on the liquid/fluid, as shown in FIG. 13. The effect ofsuch arcing/curvature of the electric current may become moresignificant (particularly in the direction of the liquid flow) as thepump is miniaturized. If the pump 110 is integrated into a flexiblethermal spreader, as described above, the need to maintain a short/smallprofile pump may be significant for maintaining the overall flexibilityof the thermal spreader.

Referring to FIG. 14, a magnetic pump 1400 for circulatingelectrically-conductive liquid within an internal flowchannel/electrically conductive cooling loop 104, in accordance with afurther exemplary embodiment of the present invention, is shown. In theillustrated embodiment, the magnetic pump 1400 (ex.—a casing of themagnetic pump, such as the ferrous casing described above) mayinclude/form an input port 1402 and an output port 1404. As describedabove, the magnetic pump 1400 may be connected to a mechanicallyflexible substrate 102 of a thermal spreader 100. Further, themechanically flexible substrate may form an internal channel 104 withinwhich electrically-conductive liquid may circulate/flow for promotingcooling properties of the thermal spreader 100. The magnetic pump 1400,may be configured for applying a magnetic field toelectrically-conductive liquid within the internal channel 104 forproviding pumping force to the liquid. Said magnetic force is appliedvia magnets 904 enclosed within the ferrous lens 906 of the pump 1400.

In the illustrated embodiment, the magnetic pump 1400/magnetic pumpcasing may include/may form a plurality of magnet flow channels 1406.The magnet flow channels 1406 may be configured/formed proximal to theoutput port 1404 of the pump. The magnetic pump 1400/magnetic pumpcasing may be further configured with channel walls 1408 for separatingthe magnet flow channels 1406. The magnet flow channels/dielectric flowstraightener channels 1406 may be configured for allowing theelectrically-conductive liquid within the internal channel to flowthrough the pump 1400 (ex.—the liquid may flow from/into the input port1402 and past/through the output port 1404 of the pump 1400) in thedirection of flow of the liquid. However, the channel walls 1408 may beconfigured for being non-electrically conductive, and thus, may furtherbe configured for preventing current flow in a direction generallyperpendicular to the direction of the flow of the liquid, therebypromoting increased or maximized pumping power/pumping efficiency forthe pump 1400. Further, the pump 1400 described in the embodiment above,by inhibiting current flow in regions of lower magnetic flux, may beeasily miniaturized for allowing said pump 1400 to be implemented in athermal spreader 100 as described above in such a manner that allows theflexibility of said mechanically flexible thermal spreader 100 to bemaintained.

Power/heat/thermal energy dissipated by electronics and other systems,such as internal combustion engines, may be transported from the heatsource to a location where said heat may be transferred to theenvironment. Said transport of heat may occur via a thermal path, suchas by conduction (ex.—via solid materials), or by convection, tofluids/liquids which travel between heat dissipating and heat absorbingsurfaces. Issues such as mechanical tolerance stack-up, maintenancerequirements, the need for vibration isolation, etc., may make itgenerally difficult to utilize a completely rigid system for saidthermal path. However, a number of compliant mechanisms for providingsaid thermal path may have less than desirable/low thermal transportproperties. The present invention describes a flexible thermal pathwhich may allow two bodies (ex.—heat source and heat sink) to remain ingood thermal contact without being mechanically affixed to each other.

As discussed above, an electrically conductive liquid cooling loop maybe formed/embedded/included within a mechanically flexible substrate.Also discussed above was the idea of integrating metallic insertswith/within the substrate at regions of high heat flux into or out ofthe substrate for minimizing overall thermal resistance.

Referring generally to FIGS. 15A, 15B, 15C and 15D, a flexible liquidcooling loop for providing a thermal path between a heat source surfaceand heat sink surface in accordance with an exemplary embodiment of thepresent invention is shown. In the illustrated embodiment, the flexiblecooling loop 1500 includes a plurality of mechanically rigid tubingsections 1502 (ex.—short, generally rectangular cross-section tubingsections, as shown in FIG. 15B). The flexible cooling loop 1500 furtherincludes a plurality of mechanically flexible tubing sections 1504. Themechanically rigid tubing sections 1502 may be connected by/heldtogether by the mechanically flexible tubing sections 1504(ex.—mechanically compliant couplings) to form the loop 1500. The loop1500 may be configured for containing a liquid (ex.—anelectrically-conductive liquid) which may be circulated within the loop1500 for promoting the transfer of thermal energy (ex.—heat) from a heatsource surface 1506 (ex.—a heat dissipating surface/hot surface) to aheat sink surface 1508 (ex.—a heat absorbing surface/cool surface) viathe loop 1500.

In further embodiments, as shown in FIG. 15C, one or more of themechanically rigid tubing sections 1502 may be configured forcontacting/being directed against/the heat source surface 1506 duringimplementation of the loop 1500. Also, one or more of the mechanicallyflexible tubing sections 1504 may be configured for contacting/beingdirected against/the heat sink surface 1508 during implementation of theloop 1500, thereby allowing the loop 1500 to provide a thermal path fordirecting heat from the heat source 1506 to the heat sink 1508. Forinstance, the loop 1500 may be positioned/sandwiched between the heatsource 1506 and the heat sink 1508. In exemplary embodiments, the rigidtubing sections 1502 of the loop 1500 may be constructed of a materialwhich promotes improved heat transfer (ex.—metal) and/or may beconstructed of a material which may provide a light/reduced weight loop(ex.—organic materials). In further embodiments, the flexible tubingsections 1504 may be constructed of flexible, rubber-like/elastomericmaterial(s).

In additional embodiments, the loop 1500 may include one or more pumps1510 (ex.—a solid-state magnetic pump). The pump 1510 may be configuredfor being connected to/integrated within/integrated into the loop viathe mechanically flexible couplings 1504. The pump 1504 may be furtherconfigured for circulating the liquid within the loop 1500 for promotingtransfer of heat from the heat source 1506 to the heat sink 1508 via theloop 1500. In embodiments in which the pump 1510 is included in/as partof the loop 1500, the liquid in the loop may not be required to beelectrically conductive. In the present invention, thepump(s)/individual pump sections 1510 may be easily fabricated andtested prior to being assembled into the rest of the loop 1500.

The loop 1500 of the present invention may be conformable to non-smoothheat sink/heat source surfaces. Consequently, the loop 1500 of thepresent invention may be less sensitive to roughness or debris of heatsink/heat source surfaces, than would be the case if, for instance, theloop-heat source surface interface were a solid-solid interface over theentire heat transfer area (ex.—an interface in which said loop was notconformable to the heat source surface).

In exemplary embodiments, the loop 1500 may further include one or morethermoelectric generators/thermoelectric modules 1512 (as shown in FIG.15D). The module(s) 1512 may be integrated into the loop 1500/connectedvia the flexible tubing sections 1504 at one or more locations/points atwhich heat is transferred into/out of the liquid cooling loop 1500. Themodules 1512 may be configured for “tapping” into part of the flow ofheat into/out of the loop for generating electrical power and providingsaid electrical power to the pump(s) 1510 for driving the pump(s) 1510to produce a net-passive device. The loop 1500 of the present inventionprovides an inherently parallel thermal path configuration whichpromotes the prevention of impeded thermal transfer to/from the loop1500, for instance, when said generator/module 1512 is implemented inthe loop 1500.

The flexible liquid cooling loop 1500 may be implemented in/integratedwithin/embedded within thermal spreader. Further, the flexible liquidcooling loop 1500 may be implemented in/integrated within/embeddedwithin a mechanically flexible substrate of a mechanically flexible,thin thermal spreader, such as one or more of the thermal spreaderembodiments described above.

In further exemplary embodiments, as shown in FIG. 16, the flexiblecooling loop 1500 may be implemented for providing a thermal path from aheat dissipating system 1602 (ex.—an electronics system) to a vehiclemounting plate 1604 (ex.—a vehicle chassis, machinery, etc.). Further, aplurality of vibration isolators 1606 may be included in a connectionbetween/for connecting said heat dissipating system 1602 and themounting plate 1604. In the scenario shown in FIG. 16, the loop 1500 mayprovide the thermal path to the mounting plate 1604, while the heatdissipating system 1602 is protected from high vibration and/or dynamicshock induced motion of the mounting plate 1604.

Referring generally to FIGS. 17A, 17B, 18A and 18B, the flexible liquidcooling loop 1500 of the present invention may have a variety ofconfigurations. For example, as shown in FIGS. 17A and 17B, the loop1500 (as illustrated in top (FIG. 17A) and side (FIG. 17B) views) may be“watchband”-style configuration, wherein said loop is conformable, forinstance, similar to a metal watchband. Further, as shown in FIGS. 18Aand 18B, the loop 1500 (as illustrated in top (FIG. 18A) and side (FIG.18B) views) may be a flat, “racetrack” configuration.

In alternative embodiments, the loop 1500 may be constructed as a singleportion of mechanically flexible tubing connected through/connecting theplurality of mechanically rigid sections 1502, allowing for a unitary,mechanically flexible tubing construction rather than implementing themultiple, mechanically flexible tubing couplings 1504.

Referring generally to FIGS. 19A (top view) and 19B (side view), aliquid cooling loop 1900 for providing a thermal path between a heatsource surface and a heat sink surface in accordance with an alternativeexemplary embodiment of the present invention is shown. The loop 1900may include a plurality of mechanically rigid tubing sections 1902.(ex—generally rectangular hollow cross-sections, as shown in FIG. 19C).Each mechanically rigid section 1902 may form a first compartment 1904and a second compartment 1906. The loop 1900 may further include aplurality of mechanically flexible tubing sections 1908. Themechanically flexible tubing sections 1908 may connect the rigidsections 1902 to form the loop 1900. For example, a first set of theflexible tubing sections 1910 may connect the rigid sections 1902 bybeing (ex.—insertably) connected into the first compartments 1904 of therigid sections 1902. Further, a second set of the flexible tubingsections 1912 may connect the rigid sections 1902 by being(ex.—insertably) connected into the second compartments 1906 of therigid sections 1902. The compartmentalized construction of the rigidsections 1902 may prevent the first set of flexible sections 1910 andsecond set of flexible sections 1912 from coming into contact with eachother, thereby segregating the liquid of the loop 1900.

A number of assembly methods may be implemented for producing the loop(1500, 1900) embodiments as described above. Individual sections may befabricated. For example, the rigid sections (ex.—metal sections) 1502may be constructed by cutting an extruded tube. The loop 1500 may thenbe assembled by connecting the individual rigid sections 1502 to theflexible sections/couplings 1504, for instance, via an adhesive.Alternatively, the loop 1500, 1900 may be constructed via additivemanufacturing, such as via an Objet Connex 500 which may print bothrigid and flexible materials in a built-up assembly.

Referring generally to FIG. 20, a mechanically flexible substrate 2000in accordance with a further alternative embodiment of the presentinvention is shown. In the illustrated embodiment, the mechanicallyflexible substrate 2000 may include/may form an internal channel 2002.For instance, the internal channel 2002 may be configured for containingelectrically-conductive liquid. The substrate 2000 may be furtherconfigured with a wall 2004, said wall 2004 being configured within theinternal channel 2002. The substrate 2000 may further include one ormore flexible bladders 2006. The bladder 2006 may be connected to thewall 2004, such that said wall 2004 may direct liquid flowing within thechannel 2002 towards the bladder 2006 as shown. The bladder 2006 may beconnected to the substrate 2000, such that said bladder 2006 may beconnected to an interior surface 2008 of the substrate 2000 (ex.—insideof the internal channel 2002, as shown in FIG. 21A, or to an exteriorsurface 2010 of the substrate 2000 (ex.—outside of the internal channel2002, as shown in FIG. 21B). Said bladder 2006 may be configured tobulge, as the liquid flowing within the internal channel 2002 exertsforce against the bladder, thereby allowing the substrate 2000 toaccount for changes in pressure due to stack-up height.

In further exemplary embodiments, as shown in FIGS. 22A and 22B, amechanically flexible substrate 2200 may be configured with one or moremicrochannels 2202. For example, microchannels 2202 may be fabricatedinto or onto the substrate 2200 via permanent photoresists. In a furtherexample, microchannels 2202 (ex.—the channel layer(s)) may be fabricatedvia permanent film-based photoresists, in which thin film barriers 2204,2206 may be applied to the flexible substrate 2200 above and below thechannel via lamination), thereby providing an inexpensive way to form asimple or complex microchannel 2202. Further, a mechanically flexiblesubstrate 2300 (ex.—the internal channel/microchannel) may beformed/constructed to minimize channel-to-chassis interconnect, as shownin FIG. 23.

It is understood that the specific order or hierarchy of steps in theforegoing disclosed methods are examples of exemplary approaches. Basedupon design preferences, it is understood that the specific order orhierarchy of steps in the method can be rearranged while remainingwithin the scope of the present invention. The accompanying methodclaims present elements of the various steps in a sample order, and arenot meant to be limited to the specific order or hierarchy presented.

It is believed that the present invention and many of its attendantadvantages will be understood by the foregoing description. It is alsobelieved that it will be apparent that various changes may be made inthe form, construction and arrangement of the components thereof withoutdeparting from the scope and spirit of the invention or withoutsacrificing all of its material advantages. The form herein beforedescribed being merely an explanatory embodiment thereof, it is theintention of the following claims to encompass and include such changes.

1. A method for fabricating a thermal spreader, comprising: laminating aplurality of layer portions together to fabricate a mechanicallyflexible substrate; providing an internal channel within themechanically flexible substrate, the internal channel configured forcontaining an electrically-conductive liquid, the internal channel beingfurther configured to allow for closed-loop flow of theelectrically-conductive liquid within the internal channel; integratinga pump with the mechanically flexible substrate; fabricating a pluralityof rigid metal inserts; forming a plurality of extension portions on asurface of each rigid metal insert included in the plurality of rigidmetal inserts; connecting the plurality of rigid metal inserts to themechanically flexible substrate; and coating an electrically-conductiveliquid contact surface of one or more of the plurality of rigid metalinserts with a layer of alkali silicate glass, theelectrically-conductive liquid contacting surface of each rigid metalinsert configured to contact the electrically-conductive liquid withinthe internal channel.
 2. A method as claimed in claim 1, furthercomprising: coating a metal portion of an electrically-conductive liquidcontact surface of the mechanically flexible substrate with a layer ofalkali silicate glass, the electrically-conductive contacting surfacesof the mechanically flexible substrate configured to contact theelectrically-conductive liquid within the internal channel.
 3. A methodas claimed in claim 1, further comprising: integrating a plurality ofpassivation metal-coated electrodes with the mechanically flexiblesubstrate.
 4. A method as claimed in claim 1, wherein the mechanicallyflexible substrate is at least partially constructed of organicmaterials.
 5. A method as claimed in claim 1, wherein the internalchannel is provided by one of: forming the internal channel within themechanically flexible substrate; and integrating the internal channelwithin the mechanically flexible substrate.
 6. A method as claimed inclaim 1, wherein the pump is configured for circulating theelectrically-conductive liquid within the internal channel.
 7. A methodas claimed in claim 1, wherein the thermal spreader is configured forbeing connected to a heat source and a heat sink, the thermal spreaderbeing further configured for directing thermal energy from the heatsource to the heat sink via the electrically-conductive liquid.
 8. Amethod as claimed in claim 1, wherein each rigid metal insert includedin the plurality of rigid metal inserts is configured for promotingthermal energy transfer to the electrically-conductive liquid and forpromoting thermal energy transfer from the electrically-conductiveliquid.
 9. A method for fabricating a plurality of thermal spreaders,comprising: laminating a plurality of layer sheets together to fabricatea mechanically flexible substrate sheet; dicing the mechanicallyflexible substrate sheet to form a plurality of mechanically flexiblesubstrates; providing an internal channel within each mechanicallyflexible substrate included in the plurality of mechanically flexiblesubstrates, each internal channel configured for containing anelectrically-conductive liquid, each internal channel being furtherconfigured to allow for closed-loop flow of the electrically-conductiveliquid within the internal channel; integrating a pump with eachmechanically flexible substrate included in the plurality ofmechanically flexible substrates fabricating a plurality of rigid metalinserts; connecting the plurality of rigid metal inserts to theplurality of mechanically flexible substrates; and coating anelectrically-conductive liquid contacting surface of one or more of theplurality of rigid metal inserts with a layer of alkali silicate glass,the electrically-conductive liquid contacting surface of each rigidmetal insert configured to contact the electrically-conductive liquidwithin each internal channel, wherein each mechanically flexiblesubstrate included in the plurality of mechanically flexible substratesis at least partially constructed of organic materials.
 10. A method asclaimed in claim 9, further comprising: forming a plurality of extensionportions on a surface of each rigid metal insert included in theplurality of rigid metal inserts.
 11. A method as claimed in claim 9,further comprising: coating a metal portion of electrically-conductiveliquid contacting surfaces of each mechanically flexible substrateincluded in the plurality of the mechanically flexible substrates with alayer of alkali silicate glass, the electrically-conductive contactingsurfaces of each mechanically flexible substrate configured to contactthe electrically-conductive liquid within the internal channel.
 12. Amethod as claimed in claim 9, further comprising: integrating aplurality of passivation metal-coated electrodes with each mechanicallyflexible substrate included in the plurality of mechanically flexiblesubstrates.
 13. A method for fabricating a plurality of thermalspreaders, comprising: laminating a plurality of layer sheets togetherto fabricate a mechanically flexible substrate sheet; dicing themechanically flexible substrate sheet to form a plurality ofmechanically flexible substrates; providing an internal channel withineach mechanically flexible substrate included in the plurality ofmechanically flexible substrates, each internal channel configured forcontaining an electrically-conductive liquid, each internal channelbeing further configured to allow for closed-loop flow of theelectrically-conductive liquid within the internal channel; integratinga pump with each mechanically flexible substrate included in theplurality of mechanically flexible substrates; fabricating a pluralityof rigid metal inserts; forming a plurality of extension portions on asurface of each rigid metal insert included in the plurality of rigidmetal inserts; connecting the plurality of rigid metal inserts to theplurality of mechanically flexible substrates; and coating anelectrically-conductive liquid contacting surface of one or more of theplurality of rigid metal inserts with a layer of alkali silicate glass,the electrically-conductive liquid contacting surface of each rigidmetal insert configured to contact the electrically-conductive liquidwithin the internal channel.
 14. A method as claimed in claim 13,further comprising: coating a metal portion of electrically-conductiveliquid contacting surfaces of each mechanically flexible substrateincluded in the plurality of the mechanically flexible substrates with alayer of alkali silicate glass, the electrically-conductive contactingsurfaces of each mechanically flexible substrate configured to contactthe electrically-conductive liquid within the internal channel.
 15. Amethod as claimed in claim 13, further comprising: integrating aplurality of passivation metal-coated electrodes with each mechanicallyflexible substrate included in the plurality of mechanically flexiblesubstrates.